大约有 6,100 项符合查询结果（耗时：0.0204秒） [XML]
Restrict varchar() column to specific values?
...t on that column which would restrict values? Something like:
CREATE TABLE SomeTable
(
Id int NOT NULL,
Frequency varchar(200),
CONSTRAINT chk_Frequency CHECK (Frequency IN ('Daily', 'Weekly', 'Monthly', 'Yearly'))
)
...
Split column at delimiter in data frame [duplicate]
... C D
Essentially, it's a fancy convenience wrapper for using read.table(text = some_character_vector, sep = some_sep) and binding that output to the original data.frame. In other words, another A base R approach could be:
df <- data.frame(ID=11:13, FOO=c('a|b','b|c','x|y'))
cbind(df, re...
How to make MySQL handle UTF-8 properly
... query/insert into the database
use DEFAULT CHARSET=utf8 when creating new tables
at this point your MySQL client and server should be in UTF-8 (see my.cnf). remember any languages you use (such as PHP) must be UTF-8 as well. Some versions of PHP will use their own MySQL client library, which may no...
PostgreSQL - max number of parameters in “IN” clause?
... possible if the inputs are all scalars (no RowExprs) and there is a
* suitable array type available. If not, we fall back to a boolean
* condition tree with multiple copies of the lefthand expression.
* Also, any IN-list items that contain Vars are handled as separate
* boolean conditions, bec...
Quick Way to Implement Dictionary in C
...ection 6.6 of The C Programming Language presents a simple dictionary (hashtable) data structure. I don't think a useful dictionary implementation could get any simpler than this. For your convenience, I reproduce the code here.
struct nlist { /* table entry: */
struct nlist *next; /* next ent...
map vs. hash_map in C++
....
hash_map (unordered_map in TR1 and Boost; use those instead) use a hash table where the key is hashed to a slot in the table and the value is stored in a list tied to that key.
map is implemented as a balanced binary search tree (usually a red/black tree).
An unordered_map should give slightly ...
PHP + MySQL transactions examples
...b_passwd,$db_name); // error-check this
// note: this is meant for InnoDB tables. won't work with MyISAM tables.
try {
$conn->autocommit(FALSE); // i.e., start transaction
// assume that the TABLE groups has an auto_increment id field
$query = "INSERT INTO groups (name) ";
$qu...
CodeIgniter activerecord, retrieve last insert id?
...
for Specific table you cannot use $this->db->insert_id() . even the last insert happened long ago it can be fetched like this. may be wrong. but working well for me
$this->db->select_max('{primary key}');
$result= $...
How to change column datatype from character to numeric in PostgreSQL 8.4
...rom old to new type.
So this might work (depending on your data):
alter table presales alter column code type numeric(10,0) using code::numeric;
-- Or if you prefer standard casting...
alter table presales alter column code type numeric(10,0) using cast(code as numeric);
This will fail if you h...
Most efficient way to remove special characters from string
...ms.
The price to pay is, of course, the initialization of the huge lookup table and keeping it in memory. Well, it's not that much data, but it's much for such a trivial function...
private static bool[] _lookup;
static Program() {
_lookup = new bool[65536];
for (char c = '0'; c <= '9'; ...